US20090035708A1 - Layer patterning using double exposure processes in a single photoresist layer - Google Patents

Layer patterning using double exposure processes in a single photoresist layer Download PDF

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Publication number
US20090035708A1
US20090035708A1 US11/831,099 US83109907A US2009035708A1 US 20090035708 A1 US20090035708 A1 US 20090035708A1 US 83109907 A US83109907 A US 83109907A US 2009035708 A1 US2009035708 A1 US 2009035708A1
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Prior art keywords
photoresist
layer
opening
parameter
value
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US7923202B2 (en
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Toshiharu Furukawa
Mark Charles Hakey
Steven John Holmes
David Vaclav Horak
Charles William Koburger, III
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GlobalFoundries Inc
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International Business Machines Corp
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Assigned to INTERNATIONAL BUSINESS MACHINES CORPORATION reassignment INTERNATIONAL BUSINESS MACHINES CORPORATION CORRECTIVE ASSIGNMENT TO CORRECT THE THE MIDDLE NAME FOR ONE OF THE INVENTORS WAS SPELLED WRONG. DAVID YACLAV HORAK SHOULD BE DAVID VACLAV HORAK PREVIOUSLY RECORDED ON REEL 019630 FRAME 0260. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT. Assignors: HAKEY, MARK CHARLES, HOLMES, STEVEN JOHN, FURUKAWA, TOSHIHARU, HORAK, DAVID VACLAV, KOBURGER III, CHARLES WILLIAM
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/20—Exposure; Apparatus therefor
    • G03F7/2022—Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure
    • G03F7/2024—Multi-step exposure, e.g. hybrid; backside exposure; blanket exposure, e.g. for image reversal; edge exposure, e.g. for edge bead removal; corrective exposure of the already developed image
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/26—Processing photosensitive materials; Apparatus therefor
    • G03F7/38—Treatment before imagewise removal, e.g. prebaking
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/26—Processing photosensitive materials; Apparatus therefor
    • G03F7/40—Treatment after imagewise removal, e.g. baking
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70425—Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning

Definitions

  • the present invention relates generally to layer patterning and more particularly to layer patterning using double exposure processes in a single photoresist layer.
  • the present invention provides a structure fabrication method, comprising providing a structure which includes (a) a to-be-patterned layer, (b) a photoresist layer on top of the to-be-patterned layer wherein the photoresist layer includes a first opening, and (c) a cap region on side walls of the first opening, wherein a first top surface of the to-be-patterned layer is exposed to a surrounding ambient through the first opening; and then performing a first lithography process resulting in a second opening in the photoresist layer, wherein the second opening is different from the first opening, and wherein a second top surface of the to-be-patterned layer is exposed to a surrounding ambient through the second opening.
  • the present invention provides a structure (and a method for forming the same) in which the double exposure processes can be carried out with pattern fidelity higher than that of the prior art.
  • FIGS. 1A-1G show cross-section views used to illustrate a fabrication process of a semiconductor structure, in accordance with embodiments of the present invention.
  • FIGS. 1A-1G show cross-section views used to illustrate a fabrication process of a semiconductor structure 100 , in accordance with embodiments of the present invention. More specifically, with reference to FIG. 1A , the fabrication process of the semiconductor structure 100 starts with a to-be-patterned layer 110 . Next, a photoresist layer 120 is formed on top of the to-be-patterned layer 110 . The photoresist layer 120 can be formed by a spin-on process followed by baking (called a post spin-on baking process).
  • Positive-tone lithography means that after a photoresist layer is exposed to light through a reticle (not shown), regions of the photoresist layer exposed to light are developed away while other regions of the photoresist layer not exposed to light remain.
  • the photoresist layer 120 is exposed to light (called a first exposure process) through a first reticle (not shown, but typically placed over the photoresist layer 120 ).
  • the reticle contains clear and opaque features such that a region 121 of the photoresist layer 120 is exposed to light while other regions of the photoresist layer 120 are not exposed to light.
  • the first exposure process also includes, after the photoresist layer 120 is exposed to light, baking the structure 100 at a high temperature (called a first post exposure baking process).
  • a first post exposure baking process photo acids created in the region 121 as a result of the first exposure process chemically react with the photoresist material of the photoresist region 121 causing the region 121 to change from insoluble to soluble in a photoresist developer.
  • the photoresist developer is used to develop away (remove) the exposed-to-light region 121 ( FIG. 1A ) of the photoresist layer 120 (called a first development process) resulting in a photoresist hole 122 in the patterned photoresist layer 120 , as shown in FIG. 1B .
  • the intensity of energy reaching the photoresist layer 120 is at its highest at the center of the region 121 and decays toward the perimeter of the region 121 .
  • a region 129 abutting the region 121 does not attain an acid concentration level required for inducing photoresist development. Therefore, when the region 121 is later removed, the region 129 remains and contains some photo acids (called residual photo acids).
  • a cap layer 130 is formed on top of the entire structure 100 of FIG. 1B by, illustratively, a spin-on process such that the cap layer 130 completely fills the photoresist hole 122 .
  • the cap layer 130 comprises a material which, when coming into direct physical contact with the residual photo acids at a high temperature, becomes (i) insoluble in a post capping rinse chemical (e.g., water) and (ii) capable of withstanding a subsequent development of the photoresist layer 120 during the formation of a photoresist hole 126 ( FIG. 1F ) in the photoresist layer 120 .
  • a post capping rinse chemical e.g., water
  • the cap layer 130 comprises a water-soluble polymer (or alcohol-soluble polymer) and can be formed by spin-applying the water-soluble polymer on top of the entire structure 100 of FIG. 1B .
  • the structure 100 is baked to an elevated temperature such that the residual photo acids in the region 129 diffuse into cap regions 133 of the cap layer 130 via the side walls 123 .
  • the diffused residual photo acids in the cap regions 133 catalyze cross-linking reactions (i.e., polymerization) in the cap regions 133 causing the cap regions 133 to change from originally soluble to insoluble in the above-mentioned post capping rinse chemical.
  • the post capping rinse chemical is used to remove the entire cap layer 130 except the insoluble cap regions 133 such that the photoresist hole 122 is reopened and such that the top surface 112 of the to-be-patterned layer 110 is again exposed to the surrounding ambient through the reopened photoresist hole 122 as shown in FIG. 1D .
  • This process can be referred to as the post capping rinse.
  • the resulting cap regions 133 cover the side walls of the original photoresist hole 122 .
  • the photoresist layer 120 is exposed to light (called a second exposure process) through a second reticle (not shown, but typically placed over the photoresist layer 120 ).
  • the second reticle contains clear and opaque features such that a region 125 of the photoresist layer 120 is exposed to light while other regions of the photoresist layer 120 are not exposed to light.
  • the second exposure process also includes, after the photoresist layer 120 is exposed to light, baking the structure 100 at a high temperature (called a second post exposure baking process).
  • a second post exposure baking process photo acids created in the region 125 as a result of the second exposure process chemically react with the photoresist material of the photoresist region 125 causing the photoresist region 125 to change from insoluble to soluble in the photoresist developer (which was used in the first development process).
  • the photoresist developer is used to develop away (remove) the exposed-to-light region 125 ( FIG. 1E ) of the photoresist layer 120 (called a second development process) resulting in a photoresist hole 126 in the patterned photoresist layer 120 , as shown in FIG. 1F .
  • the top surface 112 of the to-be-patterned layer 110 is exposed to the surrounding ambient through the photoresist hole 126 .
  • the cap regions 133 are insoluble in the photoresist developer. As a result, the side walls 123 of the original photoresist hole 122 are protected by the insoluble cap regions 133 from the second development process.
  • the to-be-patterned layer 110 is anisotropically (in the direction defined by arrows 128 ) etched with the patterned photoresist layer 120 as a blocking mask resulting in the structure 100 of FIG. 1G .
  • the same photoresist developer is used for both the first and second development processes.
  • different photoresist developers can be used in the first and second development processes, provided that the cap regions 133 are able to withstand the second development process.
  • the first and second lithography processes are positive-tone lithography.
  • each of the first and second lithography processes can be either positive-tone lithography or negative-tone lithography, provided that the cap regions 133 are able to withstand the second development process of the second lithography process.
  • the cap regions 133 are insoluble in the photoresist developer which is used in the second development process of the second lithography process, the cap regions 133 protect the side walls 123 of the photoresist hole 122 from the second development process of the second lithography process. In other words, the photoresist hole 122 which is formed in the first development process of the first lithography process is subsequently protected from the second development process of the second lithography process.
  • the first and second lithography processes are in turn performed in which the cap regions 133 are used to protect the side walls/edges 123 of the photoresist hole 122 (created by the first lithography process) from the second lithography process.
  • the cap regions 133 are not formed, and the first and second lithography processes are in turn performed such that the side walls/edges 123 of the photoresist hole 122 (resulting from the first lithography process) are not significantly affected by the second lithography process.
  • first lithography process is performed using a first dose of exposure light for the first exposure process and a first post expose bake temperature for the first post exposure baking process.
  • second lithography process is performed using a second dose of exposure light for the second exposure process and a second post expose bake temperature for the second post exposure baking process.
  • the inventors of the present invention have found that, if the first dose of exposure light is lower (or higher) than the second dose of exposure light and if the first post expose bake temperature is higher (or lower) than the second post expose bake temperature, then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed in the same conditions. For example, if (i) the first dose of exposure light is 25 mj and the first post expose bake temperature is 125° C.
  • the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed using the same first dose of exposure light and at the same first post expose bake temperature (or using the same second dose of exposure light and at the same second post expose bake temperature).
  • the first and second lithography processes are different with respect to dose of exposure light and post expose bake temperature. In an alternative embodiment, the first and second lithography processes are different with respect to dose of exposure light and developer concentration. Developer concentration is the concentration of a developer used in a development process.
  • the first lithography process is performed using a third dose of exposure light for the first exposure process and a first developer concentration for the first development process.
  • the second lithography process is performed using a fourth dose of exposure light for the second exposure process and a second developer concentration for the second development process.
  • the inventors of the present invention have found that, if the third dose of exposure light is lower (or higher) than the fourth dose of exposure light and if the first developer concentration is higher (or lower) than the second developer concentration, then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed in the same conditions.
  • the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than are in the case in which both the first and second lithography processes are performed using the same third dose of exposure light and the same first developer concentration (or using the same fourth dose of exposure light and the same second developer concentration).
  • TMAH tetramethylammonium hydroxide
  • the first and second lithography processes are (i) different with respect to dose of exposure light and post expose bake temperature and (ii) different with respect to dose of exposure light and developer concentration. In an alternative embodiment, the first and second lithography processes are different with respect to post expose bake temperature and developer concentration.
  • the first lithography process is performed using a third post expose bake temperature for the first post exposure baking process and a third developer concentration for the first development process.
  • the second lithography process is performed using a fourth post expose bake temperature for the second post exposure baking process and a fourth developer concentration for the second development process.
  • the inventors of the present invention have found that, if the third post expose bake temperature is lower (or higher) than the fourth post expose bake temperature and if the third developer concentration is higher (or lower) than the fourth developer concentration, then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed in the same conditions.
  • the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed using the same third post expose bake temperature and the same third developer concentration (or using the same fourth post expose bake temperature and the same fourth developer concentration).
  • the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed in the same conditions.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Photosensitive Polymer And Photoresist Processing (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)

Abstract

A structure and a method for forming the same. The method includes providing a structure which includes (a) a to-be-patterned layer, (b) a photoresist layer on top of the to-be-patterned layer wherein the photoresist layer includes a first opening, and (c) a cap region on side walls of the first opening. A first top surface of the to-be-patterned layer is exposed to a surrounding ambient through the first opening. The method further includes performing a first lithography process resulting in a second opening in the photoresist layer. The second opening is different from the first opening. A second top surface of the to-be-patterned layer is exposed to a surrounding ambient through the second opening.

Description

    FIELD OF THE INVENTION
  • The present invention relates generally to layer patterning and more particularly to layer patterning using double exposure processes in a single photoresist layer.
    • BACKGROUND OF THE INVENTION
  • In conventional double exposure processes, because the two exposure conditions are superimposed, the pattern fidelity is significantly degraded. Therefore, there is a need for a structure (and a method for forming the same) in which the double exposure processes can be carried out with pattern fidelity higher than that of the prior art.
    • SUMMARY OF THE INVENTION
  • The present invention provides a structure fabrication method, comprising providing a structure which includes (a) a to-be-patterned layer, (b) a photoresist layer on top of the to-be-patterned layer wherein the photoresist layer includes a first opening, and (c) a cap region on side walls of the first opening, wherein a first top surface of the to-be-patterned layer is exposed to a surrounding ambient through the first opening; and then performing a first lithography process resulting in a second opening in the photoresist layer, wherein the second opening is different from the first opening, and wherein a second top surface of the to-be-patterned layer is exposed to a surrounding ambient through the second opening.
  • The present invention provides a structure (and a method for forming the same) in which the double exposure processes can be carried out with pattern fidelity higher than that of the prior art.
    • BRIEF DESCRIPTION OF THE DRAWINGS
  • FIGS. 1A-1G show cross-section views used to illustrate a fabrication process of a semiconductor structure, in accordance with embodiments of the present invention.
    •  DETAILED DESCRIPTION OF THE INVENTION
  • FIGS. 1A-1G show cross-section views used to illustrate a fabrication process of a semiconductor structure 100, in accordance with embodiments of the present invention. More specifically, with reference to FIG. 1A, the fabrication process of the semiconductor structure 100 starts with a to-be-patterned layer 110. Next, a photoresist layer 120 is formed on top of the to-be-patterned layer 110. The photoresist layer 120 can be formed by a spin-on process followed by baking (called a post spin-on baking process).
  • In one embodiment, assume that positive-tone lithography hereafter is used. Positive-tone lithography means that after a photoresist layer is exposed to light through a reticle (not shown), regions of the photoresist layer exposed to light are developed away while other regions of the photoresist layer not exposed to light remain.
  • Next, in one embodiment, the photoresist layer 120 is exposed to light (called a first exposure process) through a first reticle (not shown, but typically placed over the photoresist layer 120). The reticle contains clear and opaque features such that a region 121 of the photoresist layer 120 is exposed to light while other regions of the photoresist layer 120 are not exposed to light.
  • In one embodiment, the first exposure process also includes, after the photoresist layer 120 is exposed to light, baking the structure 100 at a high temperature (called a first post exposure baking process). During the first post exposure baking process, photo acids created in the region 121 as a result of the first exposure process chemically react with the photoresist material of the photoresist region 121 causing the region 121 to change from insoluble to soluble in a photoresist developer.
  • Next, in one embodiment, the photoresist developer is used to develop away (remove) the exposed-to-light region 121 (FIG. 1A) of the photoresist layer 120 (called a first development process) resulting in a photoresist hole 122 in the patterned photoresist layer 120, as shown in FIG. 1B.
  • It should be noted that, with reference to FIG. 1A, during the first exposure process, the intensity of energy reaching the photoresist layer 120 is at its highest at the center of the region 121 and decays toward the perimeter of the region 121. As a result, a region 129 abutting the region 121 does not attain an acid concentration level required for inducing photoresist development. Therefore, when the region 121 is later removed, the region 129 remains and contains some photo acids (called residual photo acids).
  • Next, with reference to FIG. 1C, in one embodiment, a cap layer 130 is formed on top of the entire structure 100 of FIG. 1B by, illustratively, a spin-on process such that the cap layer 130 completely fills the photoresist hole 122.
  • In one embodiment, the cap layer 130 comprises a material which, when coming into direct physical contact with the residual photo acids at a high temperature, becomes (i) insoluble in a post capping rinse chemical (e.g., water) and (ii) capable of withstanding a subsequent development of the photoresist layer 120 during the formation of a photoresist hole 126 (FIG. 1F) in the photoresist layer 120. More specifically, in one embodiment, the cap layer 130 comprises a water-soluble polymer (or alcohol-soluble polymer) and can be formed by spin-applying the water-soluble polymer on top of the entire structure 100 of FIG. 1B.
  • Next, in one embodiment, the structure 100 is baked to an elevated temperature such that the residual photo acids in the region 129 diffuse into cap regions 133 of the cap layer 130 via the side walls 123. At the elevated temperature, the diffused residual photo acids in the cap regions 133 catalyze cross-linking reactions (i.e., polymerization) in the cap regions 133 causing the cap regions 133 to change from originally soluble to insoluble in the above-mentioned post capping rinse chemical.
  • Next, in one embodiment, the post capping rinse chemical is used to remove the entire cap layer 130 except the insoluble cap regions 133 such that the photoresist hole 122 is reopened and such that the top surface 112 of the to-be-patterned layer 110 is again exposed to the surrounding ambient through the reopened photoresist hole 122 as shown in FIG. 1D. This process can be referred to as the post capping rinse. After the post capping rinse, the resulting cap regions 133 cover the side walls of the original photoresist hole 122.
  • Next, with reference to FIG. 1E, in one embodiment, the photoresist layer 120 is exposed to light (called a second exposure process) through a second reticle (not shown, but typically placed over the photoresist layer 120). The second reticle contains clear and opaque features such that a region 125 of the photoresist layer 120 is exposed to light while other regions of the photoresist layer 120 are not exposed to light.
  • In one embodiment, the second exposure process also includes, after the photoresist layer 120 is exposed to light, baking the structure 100 at a high temperature (called a second post exposure baking process). During the second post exposure baking process, photo acids created in the region 125 as a result of the second exposure process chemically react with the photoresist material of the photoresist region 125 causing the photoresist region 125 to change from insoluble to soluble in the photoresist developer (which was used in the first development process).
  • Next, in one embodiment, the photoresist developer is used to develop away (remove) the exposed-to-light region 125 (FIG. 1E) of the photoresist layer 120 (called a second development process) resulting in a photoresist hole 126 in the patterned photoresist layer 120, as shown in FIG. 1F. The top surface 112 of the to-be-patterned layer 110 is exposed to the surrounding ambient through the photoresist hole 126. It should be noted that the cap regions 133 are insoluble in the photoresist developer. As a result, the side walls 123 of the original photoresist hole 122 are protected by the insoluble cap regions 133 from the second development process.
  • Next, in one embodiment, the to-be-patterned layer 110 is anisotropically (in the direction defined by arrows 128) etched with the patterned photoresist layer 120 as a blocking mask resulting in the structure 100 of FIG. 1G.
  • In the embodiments described above, the same photoresist developer is used for both the first and second development processes. In general, different photoresist developers can be used in the first and second development processes, provided that the cap regions 133 are able to withstand the second development process.
  • In the embodiments described above, the first and second lithography processes (that formed the original photoresist hole 122 of FIG. 1B and the photoresist hole 126 of FIG. 1F, respectively) are positive-tone lithography. In general, each of the first and second lithography processes can be either positive-tone lithography or negative-tone lithography, provided that the cap regions 133 are able to withstand the second development process of the second lithography process.
  • In summary, because the cap regions 133 are insoluble in the photoresist developer which is used in the second development process of the second lithography process, the cap regions 133 protect the side walls 123 of the photoresist hole 122 from the second development process of the second lithography process. In other words, the photoresist hole 122 which is formed in the first development process of the first lithography process is subsequently protected from the second development process of the second lithography process.
  • With reference to FIG. 1F, in the embodiments described above, the first and second lithography processes are in turn performed in which the cap regions 133 are used to protect the side walls/edges 123 of the photoresist hole 122 (created by the first lithography process) from the second lithography process. In an alternative embodiment, the cap regions 133 are not formed, and the first and second lithography processes are in turn performed such that the side walls/edges 123 of the photoresist hole 122 (resulting from the first lithography process) are not significantly affected by the second lithography process.
  • More specifically, assume that the first lithography process is performed using a first dose of exposure light for the first exposure process and a first post expose bake temperature for the first post exposure baking process. Assume further that the second lithography process is performed using a second dose of exposure light for the second exposure process and a second post expose bake temperature for the second post exposure baking process. The inventors of the present invention have found that, if the first dose of exposure light is lower (or higher) than the second dose of exposure light and if the first post expose bake temperature is higher (or lower) than the second post expose bake temperature, then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed in the same conditions. For example, if (i) the first dose of exposure light is 25 mj and the first post expose bake temperature is 125° C. and if (ii) the second dose of exposure light is 80 mj and the second post expose bake temperature is 90° C., then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed using the same first dose of exposure light and at the same first post expose bake temperature (or using the same second dose of exposure light and at the same second post expose bake temperature).
  • In the embodiments described above, the first and second lithography processes are different with respect to dose of exposure light and post expose bake temperature. In an alternative embodiment, the first and second lithography processes are different with respect to dose of exposure light and developer concentration. Developer concentration is the concentration of a developer used in a development process.
  • More specifically, assume that the first lithography process is performed using a third dose of exposure light for the first exposure process and a first developer concentration for the first development process. Assume further that the second lithography process is performed using a fourth dose of exposure light for the second exposure process and a second developer concentration for the second development process. The inventors of the present invention have found that, if the third dose of exposure light is lower (or higher) than the fourth dose of exposure light and if the first developer concentration is higher (or lower) than the second developer concentration, then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed in the same conditions. For example, if (i) the third dose of exposure light is 25 mj and the first developer is tetramethylammonium hydroxide (TMAH) with concentration of 0.26 N and if (ii) the fourth dose of exposure light is 80 mj and the second developer is TMAH with a weaker concentration than the first developer concentration such as 0.14 N, then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than are in the case in which both the first and second lithography processes are performed using the same third dose of exposure light and the same first developer concentration (or using the same fourth dose of exposure light and the same second developer concentration).
  • In the embodiments described above, the first and second lithography processes are (i) different with respect to dose of exposure light and post expose bake temperature and (ii) different with respect to dose of exposure light and developer concentration. In an alternative embodiment, the first and second lithography processes are different with respect to post expose bake temperature and developer concentration.
  • More specifically, assume that the first lithography process is performed using a third post expose bake temperature for the first post exposure baking process and a third developer concentration for the first development process. Assume further that the second lithography process is performed using a fourth post expose bake temperature for the second post exposure baking process and a fourth developer concentration for the second development process. The inventors of the present invention have found that, if the third post expose bake temperature is lower (or higher) than the fourth post expose bake temperature and if the third developer concentration is higher (or lower) than the fourth developer concentration, then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed in the same conditions. For example, if (i) the third post bake temperature is 90° C. and the third developer is TMAH with concentration of 0.26 N and if (ii) the fourth post bake temperature is 125° C. and the fourth developer is TMAH with a weaker concentration than the first developer concentration such as 0.14 N, then the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed using the same third post expose bake temperature and the same third developer concentration (or using the same fourth post expose bake temperature and the same fourth developer concentration).
  • In summary, by performing the first and second lithography processes at different values for parameters such as dose of exposure light, post expose bake temperature, and developer concentration, the side walls 123 of the photoresist hole 122 resulting from the first lithography process are affected by the second lithography process at a lower degree than in the case in which both the first and second lithography processes are performed in the same conditions.
  • While particular embodiments of the present invention have been described herein for purposes of illustration, many modifications and changes will become apparent to those skilled in the art. Accordingly, the appended claims are intended to encompass all such modifications and changes as fall within the true spirit and scope of this invention.

Claims (20)

1. A structure fabrication method, comprising:
providing a structure which includes (a) a to-be-patterned layer, (b) a photoresist layer on top of the to-be-patterned layer wherein the photoresist layer includes a first opening, and (c) a cap region on side walls of the first opening,
wherein a first top surface of the to-be-patterned layer is exposed to a surrounding ambient through the first opening; and then
performing a first lithography process resulting in a second opening in the photoresist layer,
wherein the second opening is different from the first opening, and
wherein a second top surface of the to-be-patterned layer is exposed to a surrounding ambient through the second opening.
2. The method of claim 1, further comprising, after said performing the first lithography process is performed, patterning the to-be-patterned layer with the photoresist layer as a blocking mask.
3. The method of claim 1, wherein said providing the structure comprises:
providing the to-be-patterned layer,
forming the photoresist layer on top of the to-be-patterned layer,
forming the first opening in the photoresist layer, and
forming the cap region on the side walls of the first opening.
4. The method of claim 3, wherein said forming the cap region comprises:
forming a cap layer on top of the photoresist layer such that the cap layer fills the first opening;
baking the cap layer resulting in residual photo acids diffusing from the photoresist layer into the cap layer resulting in the cap region on the side walls of the first opening,
wherein the cap region is a portion of the cap layer; and
removing the cap layer except the cap region on the side walls of the first opening.
5. The method of claim 4,
wherein said removing the cap layer comprises using a post capping rinse chemical, and
wherein the post capping rinse chemical comprises water.
6. The method of claim 3, wherein said forming the first opening comprises performing a second lithography process on the photoresist layer.
7. The method of claim 6, wherein the first and second lithography processes comprise using a same photoresist developer.
8. The method of claim 6,
wherein the first lithography process comprises using a first photoresist developer,
wherein the second lithography process comprises using a second photoresist developer, and
wherein the first photoresist developer is different from the second photoresist developer.
9. The method of claim 6,
wherein said first lithography process comprises:
performing a first exposure process, and then
performing a first development process, and
wherein said second lithography process comprises:
performing a second exposure process, and then
performing a second development process.
10. The method of claim 1,
wherein the first lithography process comprises using a first photoresist developer, and
wherein the cap region is insoluble in the first photoresist developer.
11. A structure, comprising:
(a) a to-be-patterned layer;
(b) a photoresist layer on top of the to-be-patterned layer;
(c) a first opening in the photoresist layer;
(d) a second opening in the photoresist layer; and
(e) a cap region on side walls of the first opening,
wherein the photoresist layer comprises a photoresist material,
wherein the cap region comprises a cap material,
wherein the photoresist material is different from the cap material,
wherein there is no cap region on side walls of the second opening,
wherein a first top surface of the to-be-patterned layer is exposed to a surrounding ambient through the first opening, and
wherein a second top surface of the to-be-patterned layer is exposed to the surrounding ambient through the second opening.
12. The structure of claim 11,
wherein there exists a photoresist developer which is capable of developing away portions of the photoresist layer, and
wherein the cap region is insoluble in the photoresist developer.
13. A structure fabrication method, comprising:
providing a structure which includes a to-be-patterned layer;
forming a photoresist layer on top of the to-be-patterned layer;
forming a first opening in the photoresist layer,
wherein said forming the first opening is performed under a first value of a first parameter and a first value of a second parameter; and then
forming a second opening in the photoresist layer,
wherein said forming the second opening is performed under a second value of the first parameter and a second value of the second parameter,
wherein the first value of the first parameter is lower than the second value of the first parameter, and
wherein the first value of the second parameter is higher than the second value of the second parameter.
14. The method of claim 13, further comprising, after said forming the second opening is performed, patterning the to-be-patterned layer with the photoresist layer as a blocking mask.
15. The method of claim 13,
wherein said forming the first opening comprises:
exposing the photoresist layer to light at a first dose of exposure light, then
baking the photoresist layer at a first post expose bake temperature, and then
developing the photoresist layer with a first photoresist developer having a first developer concentration, and
wherein said forming the second opening comprising:
exposing the photoresist layer to light at a second dose of exposure light, then
baking the photoresist layer at a second post expose bake temperature, and then
developing the photoresist layer with a second photoresist developer having a second developer concentration.
16. The method of claim 15,
wherein the first parameter is dose of exposure light,
wherein the first value of the first parameter is the first dose of exposure light,
wherein the second value of the first parameter is the second dose of exposure light,
wherein the second parameter is post expose bake temperature,
wherein the first value of the second parameter is the first post expose bake temperature, and
wherein the second value of the second parameter is the second post expose bake temperature.
17. The method of claim 15,
wherein the first parameter is dose of exposure light,
wherein the first value of the first parameter is the first dose of exposure light,
wherein the second value of the first parameter is the second dose of exposure light,
wherein the second parameter is developer concentration,
wherein the first value of the second parameter is the first developer concentration, and
wherein the second value of the second parameter is the second developer concentration.
18. The method of claim 15,
wherein the first parameter is post expose bake temperature,
wherein the first value of the first parameter is the first post expose bake temperature,
wherein the second value of the first parameter is the second post expose bake temperature,
wherein the second parameter is developer concentration,
wherein the first value of the second parameter is the first developer concentration, and
wherein the second value of the second parameter is the second developer concentration.
19. The method of claim 13, wherein the first and second photoresist developers are the same.
20. The method of claim 13, wherein the first photoresist developer is different from the second photoresist developer.
US11/831,099 2007-07-31 2007-07-31 Layer patterning using double exposure processes in a single photoresist layer Expired - Fee Related US7923202B2 (en)

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